Specifications

Ammonia Gas Monitor – Multi Zone
Instruction 3015-5113 49
not, the message is not passed through. The AGM-RD does not make any modifications to MODBUS
messages. It simply passes the query through to the AGM-MZ, and passes the response back to the
MODBUS master. In other words, it allows the AGM-MZs to be logically connected to the MODBUS network,
when physically they are connected to the local AGM-RD network. It is very important
to understand that the
AGM-RD will only pass messages through to the AGM-MZ when the AGM-RD is either in the “SYSTEM”
screen or the “ZONE VIEW” screen. If the AGM-RD is in any other screen
, it will return a MODBUS “busy”
exception response (exception code 06).
All AGM-RD screens, except the SYSTEM and ZONE VIEW screens, have a 10 minute timeout interval. After
This, the screen will return to the SYSTEM or ZONE VIEW screen, depending on which one was last
displayed. The AGM-RD may also be password protected so that a password entry is required in order to
view screens other than the SYSTEM or ZONE VIEW screen.
Key Comm Protocol Parameters
MODBUS Mode: RTU only
AGM-MZ Baud Rate: Default is 19,200. Programmable as defined in System data register
Parity: No Parity
Stop Bits: Default is 1. Can be set for 2 via System data register
Maximum Response Time:
4000mS when directly accessing the AGM-MZ
8,000mS when accessing the AGM-MZ through the AGM-RD.
Error Checking: CRC per MODBUS specifications
NOTE: All data
sent out from the AGM-MZ is in “little endian” byte order (Least significant byte followed by
most significant byte). This should be taken into account if the master that process the data is a “big endian”
type. Non-data information (starting address, number of points, etc.) follows normal MODBUS protocol, which
is Big Endian.